1. Field of the Invention
This invention relates to printers particularly dot-matrix types of printers. More particularly this invention relates to drop-on-demand types of dot-matrix printers, such as thermal inkjet printers in which provision is made for interchanging and identifying the printheads for the purpose of producing text or graphics in different colors and/or differing ink dot densities, sizes, for example.
2. Description of the Related Art
Inkjet printheads are used in printers and plotters. These include thermal and piezoelectric types of heads for expelling ink. The term printer and printhead as used herein is used as a term of convenience and is not intended to exclude the other types of recording such as plotting.
Thermal inkjet printers are described in the Hewlett-Packard Journal, May 1985, Volume 36, No. 5, which is included herein in its entirety by reference thereto. The production of ink drops by thermal exitation means is described in detail in terms of a specific implementation including a disposable head which could be replaced by another similar head.
As noted hereinabove there are a number of reasons for interchanging heads of different types, for example, black ink is used in most printing applications but there is a developing need for the use of colored inks in printing text and graphics. Heretofore printers having heads designed for single color printing have not been retrofited with color heads which may be interchangably fitted into the printer carriage designed for the single color head because of differing requirements resulting from printhead body configurations, ususally larger for accommodating several colors of ink, nozzle spacing and grouping, and control requirements to name a few. While multicolor heads can be provided with a chamber for black ink, where a printer is predominately used for black text or graphics, a supply of black ink in a multicolor head fitting in the printer carriage of an all black or other single color head, is limited in volume. Thus interchangeable single color/multicolor heads in a printer increase the utility of an otherwise single color printer or recorder.
Although U.S. Pat. Nos. 4,511,907; 4,540,996; 4,611,219; 4,630,076 and 4,631,548 are directed to multicolor inkjet printers, none appear to suggest or teach configurations for a multicolor head which is interchangeable with a single color head in a single color printer. Likewise, none of these patents, lacking the concept of interchangability, provide any arrangement whereby interchangeable heads each carry an identifying code for which specific printing controls are required. Thus these patents are related to this invention only in the sense of the use of individual nozzle groups for differing colors and in the employment of dot-matrix techniques for printing, but interchangability of the heads for any purpose together with their individual identities for control purposes, appear to be lacking.
Still further there appears to be no reference in the prior art with regard to the interchangability of heads in a particular printer to provide different dot densities, different drop volumes or combinations of such factors in single color and multicolor printheads.